The present invention relates to arrangements for bending tubes.
More particularly, the present invention concerns arrangements for cold bending jacketed tubes.
A jacketed tube includes an outer tube and at least one inner tube which extends inside the outer tube either coaxially or eccentrically relative thereto.
The prior art teaches arrangements for cold bending a jacketed tube in one step, if the jacketed tube includes the coaxial inner and outer tubes. The arrangement for this purpose includes at least one circular bending core and at least one mandrel. The circular core is inserted between the outer and inner tubes and it takes care of centering the outer and inner tubes relative to each other. The mandrel is inserted into the inner tube in the area of the circular core, and it is operative to provide an elongated smooth bending support inside the jacketed tube. In order to insure an axial alignment of the inner and outer tubes, the same are connected to each other at the respective end portions thereof before the bending process starts.
This method of cold bending of the jacketed tube by means of the circular core and the mandrel proved to be very efficient when the inner tube extends coaxially in the outer tube. However, this method and this arrangement as well, cannot be used when it comes to the inner tube which extends eccentrically inside the outer tube.
A method has been suggested of manufacturing a fuel filter neck which includes a jacketed tube comprising an inner tube which extends eccentrically inside an outer tube. In accordance with this method the jacketed tube is manufactured in many relatively complicated steps. Thus, at least the outer tube is bent separately and separate paths of the inner tube of flexible synthetic plastic material are consecutively introduced in the bent outer tube. Thereafter, these separate parts are arrested inside the outer tube. Thus, such a jacketed tube with the inner tube extending eccentrically inside the outer tube is stipulated by the different parts of the inner tube, by the complicated connection of these parts in the outer tube, and by separate installation of these separate parts inside the bent outer tube.